1. Field of the Invention
The disclosures herein relate to an imaging apparatus that is provided with a light transmissive filter having a plurality of polarizing filters or color separation filters arranged therein, and that produces image signals by imaging an object.
2. Description of the Related Art
In digital cameras or the like, an imaging apparatus takes an image of an object to produce image signals, and may separate the image signals into image data of different wavelength bands. In other examples, an imaging apparatus takes an image of an object to produce image signals, and may separate the image signals into image data of different polarization components. This may be performed for the purpose of enhancing the contrast of the imaged object by removing unnecessary polarization components. Such imaging apparatuses may use a light receiving device array in which light receiving devices of the same type are arranged, and may separate incoming light into light components having different polarization directions or different wavelength bands.
For example, an area-divided-type filter that has its entire area divided into plural types, each allowing the passage of light having a different characteristic, may be disposed in front of a light receiving device array such as a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like. In such imaging apparatuses, signal processing is performed with respect to image signal data output from the imaging device, so that a plurality of image signals are obtained as if light receiving devices of different types corresponding to light transmissive filters of respective, different characteristics were provided.
Further, for example, a polarizing filter may be disposed in front of a light receiving device array such as a CCD. This polarizing filter may be an area-divided polarizing filter that includes plural polarizing filters (hereinafter referred to as “polarizing filter sections”) having different polarization directions disposed in a predetermined arrangement pattern. In such an imaging apparatus, a single image signal obtained by imaging an object is separated according to polarization directions to produce plural image signals.
In another example, a color filter may be disposed in front of a light receiving device array such as a CCD. This color filter may include spectral filters (hereinafter referred to as a “spectral filter sections”) having different light transmission wavelength bands disposed in predetermined arrangement pattern as in the case of a color separation filter (i.e., area-divided spectral filter), in which areas are divided into R (red), G (green), and B (blue). In such an imaging apparatus, micro lenses may also be incorporated to produce color image signal data.
In the above-described imaging apparatus using micro lenses, a color filter, and a light receiving device array, a minute positional misalignment may occur with respect to a light incident angle, the filter position, and the micro lens position. Positional misalignment may create color shading, which refers to the phenomenon that light passing through a given filter is mixed with light passing through an adjacent filter. Matrix processing for removing mixed light may be performed a second time with respect to the data resulting from the conventional color-correction matrix processing, thereby correcting the mixing of light occurring in image signals obtained from the light receiving devices (i.e., pixels) of a light receiving device array (see Patent Document 1: Japanese Patent No. 4295149, for example).
Problems as follows are observed when image signals output from light receiving devices (i.e., pixels) of an light receiving device array are subjected to matrix processing in imaging apparatuses.
In Patent Document 1, the mixing of light caused by light passing through an adjacent filter is corrected in an imaging apparatus in which no positional misalignment is in existence between the filters and the light receiving device array. This correction is thus performed by matrix processing that uses coefficients obtained through a linear expression of coordinates of light receiving devices (i.e., pixels) after the conventional color correction matrix processing that is position-independent with respect to the light receiving device (i.e., pixels).
In the case of using an area-divided polarizing filter, a positional misalignment exceeding one pixel may occur. Under the presence of such a large misalignment, the sensitivity of light receiving devices (i.e., pixels) may become the same between pixels that are adjacent in a vertical direction or in a horizontal direction, depending on the positions of light receiving devices (i.e., pixels). Namely, weight factors for calculating a weighted sum in matrix processing may significantly differ depending on the positions of light receiving devices (i.e., pixels). Accordingly, correction cannot be made by using matrix processing that uses fixed parameters independent of the positions of light receiving devices (i.e., pixels).
Even in the case of using an area-divided polarizing filter, correction may be made by using parameters that vary depending on the positions of light receiving devices (i.e., pixels). Weight factors varying for each light receiving device (i.e., pixel) may be used, for example, to correct and reconstruct the image signals of light receiving devices (i.e., pixels) even when the positional accuracy of the area-divided filter is poor. Since parameters (i.e., weight factors) varying for each light receiving device (i.e., pixel) are used, however, there is a need for a large-size memory that can store all the parameters (i.e., weight factors).
Accordingly, it may be desirable to provide an imaging apparatus that reconstructs the image signals of light receiving devices through matrix processing, and that does not need to store all the factors of light receiving devices (i.e., pixels) in memory to perform as satisfactory a correction as when all these factors are stored.